High spin-polarization in a disordered novel quaternary Heusler alloy FeMnVGa

Abstract

In this work, we report the successful synthesis of a Fe-based novel half-metallic quaternary Heusler alloy FeMnVGa and its structural, magnetic and transport properties probed through different experimental methods and theoretical techniques. Density functional theory (DFT) calculations performed on different types of structure reveal that the structure with Ga at 4a, V at 4b, Mn at 4c and Fe at 4d (space group: F 43m) possess minimum energy among all the ordered variants. Ab-initio simulations in the most stable ordered structure show that the compound is a half-metallic ferromagnet (HMF) having a large spin-polarization (89.9 %). Neutron diffraction reveals that the compound crystalizes in disordered Type-2 structure (space group: Fm 3m) in which Ga occupies at 4a, V 4b and Fe/Mn occupy 4c/4d sites with 50:50 proportions. The structural disorder is further confirmed by X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), 57 Fe Mössbauer spectrometry results and DFT calculations. Magnetisation studies suggest that the compound orders ferromagnetically below TC ∼ 293 K and the saturation magnetization follows the Slater-Pauling rule. Mössbauer spectrometry, along with neutron diffraction suggest that Mn is the major contributor to the total magnetism in the compound, consistent with the theoretical calculations, which also indicates that spin-polarization remains high (81.3 %), even in the presence of such large atomic disorder. The robustness of the HMF property in presence of disorder is a quite unique characteristic over other reported HMF in literature and makes this compound quite promising for spintronics applications.